This disclosure relates to laminated bus bars, and methods of manufacture thereof.
The electrical power distribution system is an important component in a wide variety of applications such as computer systems, telecommunication equipment, industrial process control, automation cabinets, and the like. Power distribution bus bar systems are also key components of higher voltage applications in electric traction modules and propulsion systems for transportation, such as trains, subways, light rail vehicles, electric/hybrid cars, and the like. For such higher voltage applications, the high power bus bars are devices consisting of relatively thick (0.5 millimeter (mm) to 5 mm) conductive layers and are used to deliver electrical power at low inductance to high current devices, like the traction motors.
The high power bus bars are typically three dimensional, multilayered, and laminated. Current high power bus bars are assembled by one of four methods. The first method employs the use of thermoplastic film adhesives. In this method, two sheets of insulation film are cut to the shape of a pre-tooled dielectric layer and placed on either side of the dielectric between two or more subassemblies to form a multilayer bus bar. The bus bar is then placed in a specially designed fixture in a heated press. The entire multilayer bus bar is then heated in the press to soften the thermoplastic adhesive layers, and is held at this temperature and pressure until the bond is complete. Finally, the bus bar is removed from the press and cooled to room temperature before further handling. This process can be both time consuming (requiring between 30 and 45 minutes) and energy intensive.
A second method of high-power bus bar assembly uses a thermoset “B-staged” bondply, wherein two sheets of bondply are cut to the shape of a pre-tooled dielectric layer and placed on either side of the dielectric between two or more subassemblies to form a multilayer bus bar. The bus bar is then placed in a specially designed fixture in a heated press. The entire multilayer bus bar is heated in the press to cure the thermoset prepreg, and is held at this temperature until the cure is complete. The bus bar is then removed from the press and must cool to near room temperature before further handling. This process is also both time consuming (requiring between 1 and 2 hours) and energy intensive.
Another current method of assembling high-power bus bars uses a two component liquid epoxy or other like liquid thermoset adhesive. In this method, either the surfaces of the bus bar subassemblies or the dielectric material are coated with the liquid. This step is typically done through hand brushing of the liquid epoxy onto the surface of the subassembly and/or the dielectric. A common drawback of this method is that it can be difficult to control the thickness of the adhesive layer. Another drawback is the method is an untidy process, which requires additional labor.
An example of a bus bar produced by the above described methods is shown in FIG. 1. The bus bar 10 comprises a first subassembly 12 and a second subassembly 14. Each subassembly is disposed about a dielectric insulating board 16. An adhesive insulation layer 18, 20 is disposed between each subassembly 12, 14 and the dielectric board 16. The entire assembly is put in a press where it is heated, thereby allowing the adhesive insulation layer to form a bond between the subassemblies and the dielectric board.
In the final of the four current methods of assembling high-power bus bars, mechanical fasteners, such as nuts, bolts, rivets and the like are used to secure the subassemblies. This method requires additional hardware as well as additional labor.
There accordingly remains a need in the art for improved high-power multilayer bus bars and methods of assembling the bus bars.